-
Notifications
You must be signed in to change notification settings - Fork 10.4k
/
Copy pathCSRanking.cpp
1574 lines (1330 loc) · 55.8 KB
/
CSRanking.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
//===--- CSRanking.cpp - Constraint System Ranking ------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements solution ranking heuristics for the
// constraint-based type checker.
//
//===----------------------------------------------------------------------===//
#include "TypeChecker.h"
#include "swift/AST/GenericSignature.h"
#include "swift/AST/ParameterList.h"
#include "swift/AST/ProtocolConformance.h"
#include "swift/AST/TypeCheckRequests.h"
#include "swift/Sema/ConstraintSystem.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
using namespace swift;
using namespace constraints;
//===----------------------------------------------------------------------===//
// Statistics
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "Constraint solver overall"
STATISTIC(NumDiscardedSolutions, "Number of solutions discarded");
void ConstraintSystem::increaseScore(ScoreKind kind, unsigned value) {
if (isForCodeCompletion()) {
switch (kind) {
case SK_NonDefaultLiteral:
// Don't increase score for non-default literals in expressions involving
// a code completion. In the below example, members of EnumA and EnumB
// should be ranked equally:
// func overloaded(_ x: Float, _ y: EnumA) {}
// func overloaded(_ x: Int, _ y: EnumB) {}
// func overloaded(_ x: Float) -> EnumA {}
// func overloaded(_ x: Int) -> EnumB {}
//
// overloaded(1, .<complete>) {}
// overloaded(1).<complete>
return;
default:
break;
}
}
if (isDebugMode() && value > 0) {
if (solverState)
llvm::errs().indent(solverState->getCurrentIndent());
llvm::errs() << "(increasing '" << Score::getNameFor(kind) << "' score by "
<< value << ")\n";
}
unsigned index = static_cast<unsigned>(kind);
CurrentScore.Data[index] += value;
}
bool ConstraintSystem::worseThanBestSolution() const {
if (getASTContext().TypeCheckerOpts.DisableConstraintSolverPerformanceHacks)
return false;
if (!solverState || !solverState->BestScore ||
CurrentScore <= *solverState->BestScore)
return false;
if (isDebugMode()) {
llvm::errs().indent(solverState->getCurrentIndent())
<< "(solution is worse than the best solution)\n";
}
return true;
}
llvm::raw_ostream &constraints::operator<<(llvm::raw_ostream &out,
const Score &score) {
for (unsigned i = 0; i != NumScoreKinds; ++i) {
if (i) out << ' ';
out << score.Data[i];
}
return out;
}
///\ brief Compare two declarations for equality when they are used.
///
static bool sameDecl(Decl *decl1, Decl *decl2) {
if (decl1 == decl2)
return true;
// All types considered identical.
// FIXME: This is a hack. What we really want is to have substituted the
// base type into the declaration reference, so that we can compare the
// actual types to which two type declarations resolve. If those types are
// equivalent, then it doesn't matter which declaration is chosen.
if (isa<TypeDecl>(decl1) && isa<TypeDecl>(decl2))
return true;
if (decl1->getKind() != decl2->getKind())
return false;
return false;
}
/// Compare two overload choices for equality.
static bool sameOverloadChoice(const OverloadChoice &x,
const OverloadChoice &y) {
if (x.getKind() != y.getKind())
return false;
switch (x.getKind()) {
case OverloadChoiceKind::KeyPathApplication:
// FIXME: Compare base types after substitution?
return true;
case OverloadChoiceKind::Decl:
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaUnwrappedOptional:
case OverloadChoiceKind::DynamicMemberLookup:
case OverloadChoiceKind::KeyPathDynamicMemberLookup:
return sameDecl(x.getDecl(), y.getDecl());
case OverloadChoiceKind::TupleIndex:
return x.getTupleIndex() == y.getTupleIndex();
}
llvm_unreachable("Unhandled OverloadChoiceKind in switch.");
}
namespace {
/// Describes the relationship between the context types for two declarations.
enum class SelfTypeRelationship {
/// The types are unrelated; ignore the bases entirely.
Unrelated,
/// The types are equivalent.
Equivalent,
/// The first type is a subclass of the second.
Subclass,
/// The second type is a subclass of the first.
Superclass,
/// The first type conforms to the second
ConformsTo,
/// The second type conforms to the first.
ConformedToBy
};
} // end anonymous namespace
/// Determines whether the first type is nominally a superclass of the second
/// type, ignore generic arguments.
static bool isNominallySuperclassOf(Type type1, Type type2) {
auto nominal1 = type1->getAnyNominal();
if (!nominal1)
return false;
for (auto super2 = type2; super2; super2 = super2->getSuperclass()) {
if (super2->getAnyNominal() == nominal1)
return true;
}
return false;
}
/// Determine the relationship between the self types of the given declaration
/// contexts..
static std::pair<SelfTypeRelationship, ProtocolConformanceRef>
computeSelfTypeRelationship(DeclContext *dc, ValueDecl *decl1,
ValueDecl *decl2) {
// If both declarations are operators, even through they
// might have Self such types are unrelated.
if (decl1->isOperator() && decl2->isOperator())
return {SelfTypeRelationship::Unrelated, ProtocolConformanceRef()};
auto *dc1 = decl1->getDeclContext();
auto *dc2 = decl2->getDeclContext();
// If at least one of the contexts is a non-type context, the two are
// unrelated.
if (!dc1->isTypeContext() || !dc2->isTypeContext())
return {SelfTypeRelationship::Unrelated, ProtocolConformanceRef()};
Type type1 = dc1->getDeclaredInterfaceType();
Type type2 = dc2->getDeclaredInterfaceType();
// If the types are equal, the answer is simple.
if (type1->isEqual(type2))
return {SelfTypeRelationship::Equivalent, ProtocolConformanceRef()};
// If both types can have superclasses, which whether one is a superclass
// of the other. The subclass is the common base type.
if (type1->mayHaveSuperclass() && type2->mayHaveSuperclass()) {
if (isNominallySuperclassOf(type1, type2))
return {SelfTypeRelationship::Superclass, ProtocolConformanceRef()};
if (isNominallySuperclassOf(type2, type1))
return {SelfTypeRelationship::Subclass, ProtocolConformanceRef()};
return {SelfTypeRelationship::Unrelated, ProtocolConformanceRef()};
}
// If neither or both are protocol types, consider the bases unrelated.
bool isProtocol1 = isa<ProtocolDecl>(dc1);
bool isProtocol2 = isa<ProtocolDecl>(dc2);
if (isProtocol1 == isProtocol2)
return {SelfTypeRelationship::Unrelated, ProtocolConformanceRef()};
// Just one of the two is a protocol. Check whether the other conforms to
// that protocol.
Type protoTy = isProtocol1? type1 : type2;
Type modelTy = isProtocol1? type2 : type1;
auto proto = protoTy->castTo<ProtocolType>()->getDecl();
// If the model type does not conform to the protocol, the bases are
// unrelated.
auto conformance = dc->getParentModule()->lookupConformance(modelTy, proto);
if (conformance.isInvalid())
return {SelfTypeRelationship::Unrelated, conformance};
if (isProtocol1)
return {SelfTypeRelationship::ConformedToBy, conformance};
return {SelfTypeRelationship::ConformsTo, conformance};
}
/// Given two generic function declarations, signal if the first is more
/// "constrained" than the second by comparing the number of constraints
/// applied to each type parameter.
/// Note that this is not a subtype or conversion check - that takes place
/// in isDeclAsSpecializedAs.
static bool isDeclMoreConstrainedThan(ValueDecl *decl1, ValueDecl *decl2) {
if (decl1->getKind() != decl2->getKind() || isa<TypeDecl>(decl1))
return false;
bool bothGeneric = false;
GenericSignature sig1, sig2;
auto func1 = dyn_cast<FuncDecl>(decl1);
auto func2 = dyn_cast<FuncDecl>(decl2);
if (func1 && func2) {
bothGeneric = func1->isGeneric() && func2->isGeneric();
sig1 = func1->getGenericSignature();
sig2 = func2->getGenericSignature();
}
auto subscript1 = dyn_cast<SubscriptDecl>(decl1);
auto subscript2 = dyn_cast<SubscriptDecl>(decl2);
if (subscript1 && subscript2) {
bothGeneric = subscript1->isGeneric() && subscript2->isGeneric();
sig1 = subscript1->getGenericSignature();
sig2 = subscript2->getGenericSignature();
}
if (bothGeneric) {
auto params1 = sig1.getInnermostGenericParams();
auto params2 = sig2.getInnermostGenericParams();
if (params1.size() == params2.size()) {
for (size_t i = 0; i < params1.size(); i++) {
auto p1 = params1[i];
auto p2 = params2[i];
int np1 = static_cast<int>(sig1->getRequiredProtocols(p1).size());
int np2 = static_cast<int>(sig2->getRequiredProtocols(p2).size());
int aDelta = np1 - np2;
if (aDelta)
return aDelta > 0;
}
}
}
return false;
}
/// Determine whether one protocol extension is at least as specialized as
/// another.
static bool isProtocolExtensionAsSpecializedAs(DeclContext *dc1,
DeclContext *dc2) {
assert(dc1->getExtendedProtocolDecl());
assert(dc2->getExtendedProtocolDecl());
// If one of the protocols being extended inherits the other, prefer the
// more specialized protocol.
auto proto1 = dc1->getExtendedProtocolDecl();
auto proto2 = dc2->getExtendedProtocolDecl();
if (proto1 != proto2) {
if (proto1->inheritsFrom(proto2))
return true;
if (proto2->inheritsFrom(proto1))
return false;
}
// If the two generic signatures are identical, neither is as specialized
// as the other.
GenericSignature sig1 = dc1->getGenericSignatureOfContext();
GenericSignature sig2 = dc2->getGenericSignatureOfContext();
if (sig1.getCanonicalSignature() == sig2.getCanonicalSignature())
return false;
// Form a constraint system where we've opened up all of the requirements of
// the second protocol extension.
ConstraintSystem cs(dc1, None);
OpenedTypeMap replacements;
cs.openGeneric(dc2, sig2, ConstraintLocatorBuilder(nullptr), replacements);
// Bind the 'Self' type from the first extension to the type parameter from
// opening 'Self' of the second extension.
Type selfType1 = sig1.getGenericParams()[0];
Type selfType2 = sig2.getGenericParams()[0];
cs.addConstraint(ConstraintKind::Bind,
replacements[cast<GenericTypeParamType>(selfType2->getCanonicalType())],
dc1->mapTypeIntoContext(selfType1),
nullptr);
// Solve the system. If the first extension is at least as specialized as the
// second, we're done.
return cs.solveSingle().has_value();
}
/// Retrieve the adjusted parameter type for overloading purposes.
static Type getAdjustedParamType(const AnyFunctionType::Param ¶m) {
auto type = param.getOldType();
if (param.isAutoClosure())
return type->castTo<FunctionType>()->getResult();
return type;
}
// Is a particular parameter of a function or subscript declaration
// declared to be an IUO?
static bool paramIsIUO(const ValueDecl *decl, int paramNum) {
return swift::getParameterAt(decl, paramNum)
->isImplicitlyUnwrappedOptional();
}
/// Determine whether the first declaration is as "specialized" as
/// the second declaration.
///
/// "Specialized" is essentially a form of subtyping, defined below.
static bool isDeclAsSpecializedAs(DeclContext *dc, ValueDecl *decl1,
ValueDecl *decl2,
bool isDynamicOverloadComparison = false) {
return evaluateOrDefault(decl1->getASTContext().evaluator,
CompareDeclSpecializationRequest{
dc, decl1, decl2, isDynamicOverloadComparison},
false);
}
bool CompareDeclSpecializationRequest::evaluate(
Evaluator &eval, DeclContext *dc, ValueDecl *decl1, ValueDecl *decl2,
bool isDynamicOverloadComparison) const {
auto &C = decl1->getASTContext();
// Construct a constraint system to compare the two declarations.
ConstraintSystem cs(dc, ConstraintSystemOptions());
if (cs.isDebugMode()) {
llvm::errs() << "Comparing declarations\n";
decl1->print(llvm::errs());
llvm::errs() << "\nand\n";
decl2->print(llvm::errs());
llvm::errs() << "\n(isDynamicOverloadComparison: ";
llvm::errs() << isDynamicOverloadComparison;
llvm::errs() << ")\n";
}
auto completeResult = [&cs](bool result) {
if (cs.isDebugMode()) {
llvm::errs() << "comparison result: "
<< (result ? "better" : "not better")
<< "\n";
}
return result;
};
auto *innerDC1 = decl1->getInnermostDeclContext();
auto *innerDC2 = decl2->getInnermostDeclContext();
auto *outerDC1 = decl1->getDeclContext();
auto *outerDC2 = decl2->getDeclContext();
// If the kinds are different, there's nothing we can do.
// FIXME: This is wrong for type declarations, which we're skipping
// entirely.
if (decl1->getKind() != decl2->getKind() || isa<TypeDecl>(decl1))
return completeResult(false);
// A non-generic declaration is more specialized than a generic declaration.
if (auto func1 = dyn_cast<AbstractFunctionDecl>(decl1)) {
auto func2 = cast<AbstractFunctionDecl>(decl2);
if (func1->isGeneric() != func2->isGeneric())
return completeResult(func2->isGeneric());
}
if (auto subscript1 = dyn_cast<SubscriptDecl>(decl1)) {
auto subscript2 = cast<SubscriptDecl>(decl2);
if (subscript1->isGeneric() != subscript2->isGeneric())
return completeResult(subscript2->isGeneric());
}
// Members of protocol extensions have special overloading rules.
ProtocolDecl *inProtocolExtension1 = outerDC1->getExtendedProtocolDecl();
ProtocolDecl *inProtocolExtension2 = outerDC2->getExtendedProtocolDecl();
if (inProtocolExtension1 && inProtocolExtension2) {
// Both members are in protocol extensions.
// Determine whether the 'Self' type from the first protocol extension
// satisfies all of the requirements of the second protocol extension.
bool better1 = isProtocolExtensionAsSpecializedAs(outerDC1, outerDC2);
bool better2 = isProtocolExtensionAsSpecializedAs(outerDC2, outerDC1);
if (better1 != better2) {
return completeResult(better1);
}
} else if (inProtocolExtension1 || inProtocolExtension2) {
// One member is in a protocol extension, the other is in a concrete type.
// Prefer the member in the concrete type.
return completeResult(inProtocolExtension2);
}
// A concrete type member is always more specialised than a protocol
// member (bearing in mind that we have already handled the case where
// exactly one member is in a protocol extension). Only apply this rule in
// Swift 5 mode to better maintain source compatibility under Swift 4
// mode.
//
// Don't apply this rule when comparing two overloads found through
// dynamic lookup to ensure we keep cases like this ambiguous:
//
// @objc protocol P {
// var i: String { get }
// }
// class C {
// @objc var i: Int { return 0 }
// }
// func foo(_ x: AnyObject) {
// x.i // ensure ambiguous.
// }
//
if (C.isSwiftVersionAtLeast(5) && !isDynamicOverloadComparison) {
auto inProto1 = isa<ProtocolDecl>(outerDC1);
auto inProto2 = isa<ProtocolDecl>(outerDC2);
if (inProto1 != inProto2)
return completeResult(inProto2);
}
Type type1 = decl1->getInterfaceType();
Type type2 = decl2->getInterfaceType();
// Add curried 'self' types if necessary.
if (!decl1->hasCurriedSelf())
type1 = type1->addCurriedSelfType(outerDC1);
if (!decl2->hasCurriedSelf())
type2 = type2->addCurriedSelfType(outerDC2);
auto openType = [&](ConstraintSystem &cs, DeclContext *innerDC,
DeclContext *outerDC, Type type,
OpenedTypeMap &replacements,
ConstraintLocator *locator) -> Type {
if (auto *funcType = type->getAs<AnyFunctionType>()) {
return cs.openFunctionType(funcType, locator, replacements, outerDC);
}
cs.openGeneric(outerDC, innerDC->getGenericSignatureOfContext(), locator,
replacements);
return cs.openType(type, replacements);
};
bool knownNonSubtype = false;
auto *locator = cs.getConstraintLocator({});
// FIXME: Locator when anchored on a declaration.
// Get the type of a reference to the second declaration.
OpenedTypeMap unused, replacements;
auto openedType2 = openType(cs, innerDC1, outerDC2, type2, unused, locator);
auto openedType1 =
openType(cs, innerDC2, outerDC1, type1, replacements, locator);
for (const auto &replacement : replacements) {
if (auto mapped = innerDC1->mapTypeIntoContext(replacement.first)) {
cs.addConstraint(ConstraintKind::Bind, replacement.second, mapped,
locator);
}
}
// Extract the self types from the declarations, if they have them.
auto getSelfType = [](AnyFunctionType *fnType) -> Type {
auto params = fnType->getParams();
assert(params.size() == 1);
return params.front().getPlainType()->getMetatypeInstanceType();
};
Type selfTy1;
Type selfTy2;
if (outerDC1->isTypeContext()) {
auto funcTy1 = openedType1->castTo<FunctionType>();
selfTy1 = getSelfType(funcTy1);
openedType1 = funcTy1->getResult();
}
if (outerDC2->isTypeContext()) {
auto funcTy2 = openedType2->castTo<FunctionType>();
selfTy2 = getSelfType(funcTy2);
openedType2 = funcTy2->getResult();
}
// Determine the relationship between the 'self' types and add the
// appropriate constraints. The constraints themselves never fail, but
// they help deduce type variables that were opened.
auto selfTypeRelationship = computeSelfTypeRelationship(dc, decl1, decl2);
auto relationshipKind = selfTypeRelationship.first;
auto conformance = selfTypeRelationship.second;
(void)conformance;
switch (relationshipKind) {
case SelfTypeRelationship::Unrelated:
// Skip the self types parameter entirely.
break;
case SelfTypeRelationship::Equivalent:
cs.addConstraint(ConstraintKind::Bind, selfTy1, selfTy2, locator);
break;
case SelfTypeRelationship::Subclass:
cs.addConstraint(ConstraintKind::Subtype, selfTy1, selfTy2, locator);
break;
case SelfTypeRelationship::Superclass:
cs.addConstraint(ConstraintKind::Subtype, selfTy2, selfTy1, locator);
break;
case SelfTypeRelationship::ConformsTo:
assert(conformance);
cs.addConstraint(ConstraintKind::ConformsTo, selfTy1,
cast<ProtocolDecl>(outerDC2)->getDeclaredInterfaceType(),
locator);
break;
case SelfTypeRelationship::ConformedToBy:
assert(conformance);
cs.addConstraint(ConstraintKind::ConformsTo, selfTy2,
cast<ProtocolDecl>(outerDC1)->getDeclaredInterfaceType(),
locator);
break;
}
bool fewerEffectiveParameters = false;
if (!decl1->hasParameterList() && !decl2->hasParameterList()) {
// If neither decl has a parameter list, simply check whether the first
// type is a subtype of the second.
cs.addConstraint(ConstraintKind::Subtype, openedType1, openedType2,
locator);
} else if (decl1->hasParameterList() && decl2->hasParameterList()) {
// Otherwise, check whether the first function type's input is a subtype
// of the second type's inputs, i.e., can we forward the arguments?
auto funcTy1 = openedType1->castTo<FunctionType>();
auto funcTy2 = openedType2->castTo<FunctionType>();
auto params1 = funcTy1->getParams();
auto params2 = funcTy2->getParams();
unsigned numParams1 = params1.size();
unsigned numParams2 = params2.size();
if (numParams1 > numParams2)
return completeResult(false);
// If they both have trailing closures, compare those separately.
bool compareTrailingClosureParamsSeparately = false;
if (numParams1 > 0 && numParams2 > 0 &&
params1.back().getParameterType()->is<AnyFunctionType>() &&
params2.back().getParameterType()->is<AnyFunctionType>()) {
compareTrailingClosureParamsSeparately = true;
}
auto maybeAddSubtypeConstraint =
[&](const AnyFunctionType::Param ¶m1,
const AnyFunctionType::Param ¶m2) -> bool {
// If one parameter is variadic and the other is not...
if (param1.isVariadic() != param2.isVariadic()) {
// If the first parameter is the variadic one, it's not
// more specialized.
if (param1.isVariadic())
return false;
fewerEffectiveParameters = true;
}
Type paramType1 = getAdjustedParamType(param1);
Type paramType2 = getAdjustedParamType(param2);
// Check whether the first parameter is a subtype of the second.
cs.addConstraint(ConstraintKind::Subtype, paramType1, paramType2,
locator);
return true;
};
auto pairMatcher = [&](unsigned idx1, unsigned idx2) -> bool {
// Emulate behavior from when IUO was a type, where IUOs
// were considered subtypes of plain optionals, but not
// vice-versa. This wouldn't normally happen, but there are
// cases where we can rename imported APIs so that we have a
// name collision, and where the parameter type(s) are the
// same except for details of the kind of optional declared.
auto param1IsIUO = paramIsIUO(decl1, idx1);
auto param2IsIUO = paramIsIUO(decl2, idx2);
if (param2IsIUO && !param1IsIUO)
return false;
if (!maybeAddSubtypeConstraint(params1[idx1], params2[idx2]))
return false;
return true;
};
ParameterListInfo paramInfo(params2, decl2, decl2->hasCurriedSelf());
auto params2ForMatching = params2;
if (compareTrailingClosureParamsSeparately) {
--numParams1;
params2ForMatching = params2.drop_back();
}
InputMatcher IM(params2ForMatching, paramInfo);
if (IM.match(numParams1, pairMatcher) != InputMatcher::IM_Succeeded)
return completeResult(false);
fewerEffectiveParameters |= (IM.getNumSkippedParameters() != 0);
if (compareTrailingClosureParamsSeparately)
if (!maybeAddSubtypeConstraint(params1.back(), params2.back()))
knownNonSubtype = true;
}
if (!knownNonSubtype) {
// Solve the system.
auto solution = cs.solveSingle(FreeTypeVariableBinding::Allow);
// Ban value-to-optional conversions.
if (solution && solution->getFixedScore().Data[SK_ValueToOptional] == 0)
return completeResult(true);
}
// If the first function has fewer effective parameters than the
// second, it is more specialized.
if (fewerEffectiveParameters)
return completeResult(true);
return completeResult(false);
}
Comparison TypeChecker::compareDeclarations(DeclContext *dc,
ValueDecl *decl1,
ValueDecl *decl2){
bool decl1Better = isDeclAsSpecializedAs(dc, decl1, decl2);
bool decl2Better = isDeclAsSpecializedAs(dc, decl2, decl1);
if (decl1Better == decl2Better)
return Comparison::Unordered;
return decl1Better ? Comparison::Better : Comparison::Worse;
}
static Type getUnlabeledType(Type type, ASTContext &ctx) {
return type.transform([&](Type type) -> Type {
if (auto *tupleType = dyn_cast<TupleType>(type.getPointer())) {
if (tupleType->getNumElements() == 1)
return ParenType::get(ctx, tupleType->getElementType(0));
SmallVector<TupleTypeElt, 8> elts;
for (auto elt : tupleType->getElements()) {
elts.push_back(elt.getWithoutName());
}
return TupleType::get(elts, ctx);
}
return type;
});
}
static void addKeyPathDynamicMemberOverloads(
ArrayRef<Solution> solutions, unsigned idx1, unsigned idx2,
SmallVectorImpl<SolutionDiff::OverloadDiff> &overloadDiff) {
const auto &overloads1 = solutions[idx1].overloadChoices;
const auto &overloads2 = solutions[idx2].overloadChoices;
for (auto &entry : overloads1) {
auto *locator = entry.first;
if (!locator->isForKeyPathDynamicMemberLookup())
continue;
auto overload2 = overloads2.find(locator);
if (overload2 == overloads2.end())
continue;
auto &overloadChoice1 = entry.second.choice;
auto &overloadChoice2 = overload2->second.choice;
SmallVector<OverloadChoice, 4> choices;
choices.resize(solutions.size());
choices[idx1] = overloadChoice1;
choices[idx2] = overloadChoice2;
overloadDiff.push_back(
SolutionDiff::OverloadDiff{locator, std::move(choices)});
}
}
namespace {
/// A set of type variable bindings to compare for ranking.
struct TypeBindingsToCompare {
Type Type1;
Type Type2;
// These bits are used in the case where we need to compare a lone unlabeled
// parameter with a labeled parameter, and allow us to prefer the unlabeled
// one.
bool Type1WasLabeled = false;
bool Type2WasLabeled = false;
TypeBindingsToCompare(Type type1, Type type2)
: Type1(type1), Type2(type2) {}
/// Whether the type bindings to compare are known to be the same.
bool areSameTypes() const {
return !Type1WasLabeled && !Type2WasLabeled && Type1->isEqual(Type2);
}
};
} // end anonymous namespace
/// Given the bound types of two constructor overloads, returns their parameter
/// list types as tuples to compare for solution ranking, or \c None if they
/// shouldn't be compared.
static Optional<TypeBindingsToCompare>
getConstructorParamsAsTuples(ASTContext &ctx, Type boundTy1, Type boundTy2) {
auto choiceTy1 =
boundTy1->lookThroughAllOptionalTypes()->getAs<FunctionType>();
auto choiceTy2 =
boundTy2->lookThroughAllOptionalTypes()->getAs<FunctionType>();
// If the type variables haven't been bound to functions yet, let's not try
// and rank them.
if (!choiceTy1 || !choiceTy2)
return None;
auto initParams1 = choiceTy1->getParams();
auto initParams2 = choiceTy2->getParams();
if (initParams1.size() != initParams2.size())
return None;
// Don't compare if there are variadic differences. This preserves the
// behavior of when we'd compare through matchTupleTypes with the parameter
// flags intact.
for (auto idx : indices(initParams1)) {
if (initParams1[idx].isVariadic() != initParams2[idx].isVariadic())
return None;
}
// Awful hack needed to preserve source compatibility: If we have single
// variadic parameters to compare, where one has a label and the other does
// not, e.g (x: Int...) and (Int...), compare the parameter types by
// themselves, and make a note of which one has the label.
//
// This is needed because previously we would build a TupleType for a single
// unlabeled variadic parameter (Int...), which would let us compare it with
// a labeled parameter (x: Int...) and prefer the unlabeled version. With the
// parameter flags stripped however, (Int...) would become a paren type,
// which we wouldn't compare with the tuple type (x: Int...). To preserve the
// previous behavior in this case, just do a type comparison for the param
// types, and record where we stripped a label. The ranking logic can then use
// this to prefer the unlabeled variant. This is only needed in the single
// parameter case, as other cases will compare as tuples the same as before.
// In cases where variadics aren't used, we may end up trying to compare
// parens with tuples, but that's consistent with what we previously did.
//
// Note we can just do checks on initParams1, as we've already established
// sizes and variadic bits are consistent.
if (initParams1.size() == 1 && initParams1[0].isVariadic() &&
initParams1[0].hasLabel() != initParams2[0].hasLabel()) {
TypeBindingsToCompare bindings(initParams1[0].getParameterType(),
initParams2[0].getParameterType());
if (initParams1[0].hasLabel()) {
bindings.Type1WasLabeled = true;
} else {
bindings.Type2WasLabeled = true;
}
return bindings;
}
auto tuple1 = AnyFunctionType::composeTuple(
ctx, initParams1, ParameterFlagHandling::IgnoreNonEmpty);
auto tuple2 = AnyFunctionType::composeTuple(
ctx, initParams2, ParameterFlagHandling::IgnoreNonEmpty);
return TypeBindingsToCompare(tuple1, tuple2);
}
SolutionCompareResult ConstraintSystem::compareSolutions(
ConstraintSystem &cs, ArrayRef<Solution> solutions,
const SolutionDiff &diff, unsigned idx1, unsigned idx2) {
if (cs.isDebugMode()) {
llvm::errs().indent(cs.solverState->getCurrentIndent())
<< "comparing solutions " << idx1 << " and " << idx2 << "\n";
}
// Whether the solutions are identical.
bool identical = true;
// Compare the fixed scores by themselves.
if (solutions[idx1].getFixedScore() != solutions[idx2].getFixedScore()) {
return solutions[idx1].getFixedScore() < solutions[idx2].getFixedScore()
? SolutionCompareResult::Better
: SolutionCompareResult::Worse;
}
// Compute relative score.
unsigned score1 = 0;
unsigned score2 = 0;
auto foundRefinement1 = false;
auto foundRefinement2 = false;
bool isStdlibOptionalMPlusOperator1 = false;
bool isStdlibOptionalMPlusOperator2 = false;
bool isVarAndNotProtocol1 = false;
bool isVarAndNotProtocol2 = false;
auto getWeight = [&](ConstraintLocator *locator) -> unsigned {
if (auto *anchor = locator->getAnchor().dyn_cast<Expr *>()) {
auto weight = cs.getExprDepth(anchor);
if (weight)
return *weight + 1;
}
return 1;
};
SmallVector<SolutionDiff::OverloadDiff, 4> overloadDiff(diff.overloads);
// Single type of keypath dynamic member lookup could refer to different
// member overloads, we have to do a pair-wise comparison in such cases
// otherwise ranking would miss some viable information e.g.
// `_ = arr[0..<3]` could refer to subscript through writable or read-only
// key path and each of them could also pick overload which returns `Slice<T>`
// or `ArraySlice<T>` (assuming that `arr` is something like `Box<[Int]>`).
addKeyPathDynamicMemberOverloads(solutions, idx1, idx2, overloadDiff);
// Compare overload sets.
for (auto &overload : overloadDiff) {
unsigned weight = getWeight(overload.locator);
auto choice1 = overload.choices[idx1];
auto choice2 = overload.choices[idx2];
// If the systems made the same choice, there's nothing interesting here.
if (sameOverloadChoice(choice1, choice2))
continue;
// If constraint system is underconstrained e.g. because there are
// editor placeholders, it's possible to end up with multiple solutions
// where each ambiguous declaration is going to have its own overload kind:
//
// func foo(_: Int) -> [Int] { ... }
// func foo(_: Double) -> (result: String, count: Int) { ... }
//
// _ = foo(<#arg#>).count
//
// In this case solver would produce 2 solutions: one where `count`
// is a property reference on `[Int]` and another one is tuple access
// for a `count:` element.
if (choice1.isDecl() != choice2.isDecl())
return SolutionCompareResult::Incomparable;
auto decl1 = choice1.getDecl();
auto dc1 = decl1->getDeclContext();
auto decl2 = choice2.getDecl();
auto dc2 = decl2->getDeclContext();
// The two systems are not identical. If the decls in question are distinct
// protocol members, let the checks below determine if the two choices are
// 'identical' or not. This allows us to structurally unify disparate
// protocol members during overload resolution.
// FIXME: Along with the FIXME below, this is a hack to work around
// problems with restating requirements in protocols.
identical = false;
bool decl1InSubprotocol = false;
bool decl2InSubprotocol = false;
if (dc1->getContextKind() == DeclContextKind::GenericTypeDecl &&
dc1->getContextKind() == dc2->getContextKind()) {
auto pd1 = dyn_cast<ProtocolDecl>(dc1);
auto pd2 = dyn_cast<ProtocolDecl>(dc2);
// FIXME: This hack tells us to prefer members of subprotocols over
// those of the protocols they inherit, if all else fails.
// If we were properly handling overrides of protocol members when
// requirements get restated, it would not be necessary.
if (pd1 && pd2 && pd1 != pd2) {
identical = true;
decl1InSubprotocol = pd1->inheritsFrom(pd2);
decl2InSubprotocol = pd2->inheritsFrom(pd1);
}
}
// If the kinds of overload choice don't match...
if (choice1.getKind() != choice2.getKind()) {
identical = false;
// A declaration found directly beats any declaration found via dynamic
// lookup, bridging, or optional unwrapping.
if ((choice1.getKind() == OverloadChoiceKind::Decl) &&
(choice2.getKind() == OverloadChoiceKind::DeclViaDynamic ||
choice2.getKind() == OverloadChoiceKind::DeclViaBridge ||
choice2.getKind() == OverloadChoiceKind::DeclViaUnwrappedOptional)) {
score1 += weight;
continue;
}
if ((choice1.getKind() == OverloadChoiceKind::DeclViaDynamic ||
choice1.getKind() == OverloadChoiceKind::DeclViaBridge ||
choice1.getKind() == OverloadChoiceKind::DeclViaUnwrappedOptional) &&
choice2.getKind() == OverloadChoiceKind::Decl) {
score2 += weight;
continue;
}
if (choice1.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup) {
if (choice2.getKind() == OverloadChoiceKind::DynamicMemberLookup)
// Dynamic member lookup through a keypath is better than one using
// string because it carries more type information.
score1 += weight;
else
// Otherwise let's prefer non-dynamic declaration.
score2 += weight;
continue;
}
if (choice2.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup) {
if (choice1.getKind() == OverloadChoiceKind::DynamicMemberLookup)
// Dynamic member lookup through a keypath is better than one using
// string because it carries more type information.
score2 += weight;
else
// Otherwise let's prefer non-dynamic declaration.
score1 += weight;
continue;
}
continue;
}
// The kinds of overload choice match, but the contents don't.
switch (choice1.getKind()) {
case OverloadChoiceKind::TupleIndex:
continue;
case OverloadChoiceKind::KeyPathApplication:
llvm_unreachable("Never considered different");
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::Decl:
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaUnwrappedOptional:
case OverloadChoiceKind::DynamicMemberLookup:
case OverloadChoiceKind::KeyPathDynamicMemberLookup:
break;
}
// We don't apply some ranking rules to overloads found through dynamic
// lookup in order to keep a few potentially ill-formed cases ambiguous.
bool isDynamicOverloadComparison =
choice1.getKind() == OverloadChoiceKind::DeclViaDynamic &&
choice2.getKind() == OverloadChoiceKind::DeclViaDynamic;
// Determine whether one declaration is more specialized than the other.
bool firstAsSpecializedAs = false;
bool secondAsSpecializedAs = false;
if (isDeclAsSpecializedAs(cs.DC, decl1, decl2,
isDynamicOverloadComparison)) {
score1 += weight;
firstAsSpecializedAs = true;
}
if (isDeclAsSpecializedAs(cs.DC, decl2, decl1,
isDynamicOverloadComparison)) {
score2 += weight;
secondAsSpecializedAs = true;
}
// If each is as specialized as the other, and both are constructors,
// check the constructor kind.
if (firstAsSpecializedAs && secondAsSpecializedAs) {
if (auto ctor1 = dyn_cast<ConstructorDecl>(decl1)) {
if (auto ctor2 = dyn_cast<ConstructorDecl>(decl2)) {
if (ctor1->getInitKind() != ctor2->getInitKind()) {
if (ctor1->getInitKind() < ctor2->getInitKind())